Global regulation by proteolysis in Escherichia coli: Molecular recognition, signal integration and quantitative analysis of proteolysis-controlled regulatory circuits

某些关键调节因子的细胞量是合成和降解调节之间高度动态和调节平衡的结果。使用大肠杆菌中RNA聚合酶的Sigma-S亚基的多重应激抑制的蛋白水解作为模型系统，这里提交的提案集中在调节蛋白水解领域中的两个主要未解决的问题：（i）通过蛋白水解机制的选择性底物识别的分子细节，以及（ii）将环境应激条件与关键细胞调节因子的蛋白水解速率相联系的信号转导途径。Sigma-S由识别因子RssB直接靶向，RssB对Sigma-S（a2.5）内的小区域的亲和力由磷酸化控制。然后RssB将Sigma-S转移到ClpXP蛋白酶，在那里Sigma-S被快速完全降解。将研究Sigma-S（可能还有Sigma-70）中蛋白水解识别位点与各种识别因子和分子伴侣（RssB，ClpX，ClpA）之间的分子相互作用。此外，信号转导途径，抑制Sigma-S营业额在各种压力条件下将阐明。这些途径分别控制RssB磷酸化和/或Sigma-S和ClpXP的竞争结合配偶体（例如核心RNA聚合酶或替代ClpXP底物）的细胞量和与它们的相互作用。这些研究应该提供重要的新的见解调节蛋白水解，以及复杂的细菌信号整合网络一般。

The cellular amount of certain key regulatory factors is the result of a highly dynamic and regulated balance between regulation of synthesis and degradation. Using the multiple stress-inhibited proteolysis of the Sigma-S subunit of RNA polymerase in E.coli as a model system, the proposal submitted here focusses on the two major unsolved problems in the field of regulated proteolysis: (i) the molecular details of selective substrate recognition by the proteolytic machinery, and (ii) the signal transduction pathways that connect environmental stress conditions to the rate of proteolysis of a key cellular regulator. Sigma-S is directly targeted by a recognition factor, RssB, whose affinity for a small region within Sigma-S (a2.5) is controlled by phosphorylation. RssB then transfers Sigma-S to the ClpXP protease, where Sigma-S is rapidly and completely degraded. Molecular interactions between proteolytic recognition sites in Sigma-S (and probably in Sigma-70) and various recognizing factors and chaperones (RssB, ClpX, ClpA) will be studied. In addition, the signal transduction pathways that inhibit Sigma-S turnover in response to various stress conditions will be elucidated. These pathways either control RssB phosphorylation and/or the cellular amount of and interaction with competing binding partners for Sigma-S and ClpXP, such as core RNA polymerase or alternative ClpXP substrates, respectively. These studies should provide important novel insights into regulated proteolysis as well as into complex bacterial signal integration networks in general.